docs: def model_loader(gem_file_path, gem_file_type):
      """Consolidated function to load a GEM using COBRApy. Specify the file type being loaded.
  
      Args:
          gem_file_path (str): Path to model file
          gem_file_type (str): GEM model type - ``sbml`` (or ``xml``), ``mat``, or ``json`` format
  
      Returns:
          COBRApy Model object.
  
      """
  
      if gem_file_type.lower() == 'xml' or gem_file_type.lower() == 'sbml':
          model = read_sbml_model(gem_file_path)
      elif gem_file_type.lower() == 'mat':
          model = load_matlab_model(gem_file_path)
      elif gem_file_type.lower() == 'json':
          model = load_json_model(gem_file_path)
      else:
          raise ValueError('File type must be "sbml", "xml", "mat", or "json".')
  
      return model